1. Field of the Invention
The present invention relates to methods of conducting catalytic chemical reactions under conditions so as to minimize or substantially avoid deactivation of the catalyst material due to a reaction of polar components, i.e. nitrogenous substances, which may be present in the hydrocarbon feedstream with the catalyst material.
More particularly, the present invention relates to the preparation of alkyl tertiary alkyl ether by catalytic reaction of hydrocarbon streams containing mixtures of isoolefins and alcohols under conditions which minimize or substantially avoid reaction of the catalytic material in the catalytic reaction zone with any nitrogenous components which may be present in the stream.
Specifically, the present invention is directed to a catalytic reaction for producing alkyl tertiary alkyl ether which involves removing nitrogenous components from the hydrocarbon stream prior to introduction of the stream into the catalytic reaction zone to inhibit reaction of the nitrogenous components which may be present in the stream with the catalyst material.
2. Discussion of Background and Material Information
As a general matter, processes are known whereby specific hydrocarbon fractions may be purified using solid adsorbents. In these prior art processes a bed of a solid adsorbent material is contacted with a hydrocarbon stream in either liquid or vapor phase under conditions favorable to adsorption. During contacting, a minor portion of the hydrocarbon stream, including contaminants, is adsorbed into pores in the solid adsorbent, while the major portion, which may be termed the effluent or raffinate, passes through for subsequent processing.
Depending on the process and the product involved, the adsorbent may be used either to adsorb the desired product, which is then desorbed and recovered, or to adsorb the undesired contaminants, to result in an effluent which is the purified product, as is the intended goal of the present invention.
The efficiency of the adsorption is determined by several factors, including the precise adsorbent selected, the contaminants to be adsorbed, temperature, pressure, flow rate of the hydrocarbon stream, and concentrations of feedstream components.
The prior art in this area demonstrates the complexity and the high degree of specificity involved in matching a given feedstock, containing given contaminants, from which a certain product is desired, with a suitable adsorbent under appropriate conditions to arrive at a commercially acceptable process.
U.S. Pat. No. 4,831,206, ZARCHY, is directed to a process for removing deleterious components, for example, nitrogen-containing substances, from a fluid stream wherein the feedstream containing the deleterious components is contacted with a sorbent while in the vapor phase which is capable of selectively removing the deleterious component as compared to the remaining components contained within the feedstream and then, while still maintaining the feedstream in the vapor phase, subjecting the feedstream effluent, now having a reduced concentration of the deleterious component, to the step of the processing operation which is sensitive to the deleterious component, which step is carried out in the vapor phase at conditions suitable for such step. The ZARCHY patent emphasizes that for purposes of his invention, the hydrocarbon feed which may contain sulfide and/or ammonia is maintained in the vapor phase as it is passed through the adsorption zone at temperatures which are well above the dew point of the feedstream, generally in the range of about 250.degree. F. to about 600.degree. F.
U.S. Pat. No. 4,831,207, O'KEEFE et al., is directed to a process similar to the one disclosed by ZARCHY, which utilizes two adsorption zones to provide for continuity of the adsorption step which are switched or cycled in service at intervals that would preclude breakthrough of the adsorbed deleterious component. A disclosed advantage is that the fluid feedstream containing one or more of the deleterious components, such as nitrogen-containing substances, can continuously flow through an adsorption zone, the effluent from which can flow continuously to at least the sensitive step of the process, and at least a portion thereof can be passed continuously to a desorption zone. At an appropriate point in time, i.e., when the adsorption zone is substantially laden with the deleterious component and before there is any breakthrough, the adsorption zone is switched to become a desorption zone, and the desorption zone is then switched to become an adsorption zone in conjunction with the proper switching of the feedstream flow path.
Notwithstanding attempts to improve the production of isobutene and MTBE, a problem associated with conventional processes for the production of MTBE is that the catalyst material used in the catalyst reaction processes has a tendency to deactivate in an unacceptably short period of time.